A handout picture released by the Syrian Arab News Agency (SANA) on September 22, 2016, shows a humanitarian convoy delivering aid in the militant-held town of Moadamiyet al-Sham, on the southwestern outskirts of Damascus. (Via AFP)

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) says all sides of the conflict in Syria’s Aleppo have to back an extended ceasefire in order for the UN body to provide assistance for the besieged civilians in the city.

Jens Laerke, the OCHA spokesman, said in Geneva, Switzerland, on Wednesday that a time-bound deal would not be sufficient for the UN teams to mobilize to deliver aid to the militant-held eastern part of Aleppo.

"Before we can do something really meaningful... we need assurances from all parties," Laerke said, adding, “We need a minimum of 48 hours.”

UN and Red Cross trucks packed with aid for eastern Aleppo are waiting near the Turkish border for guarantees that they can safely make deliveries of humanitarian aid.

On Tuesday, the Syrian government and Russia halted airstrikes on Aleppo for eight hours to allow civilians and militants not affiliated with terrorists to leave the city.

Russian Defense Minister Sergey Shoigu said the halt should help pave the way for foreign-backed militants to leave the eastern parts of the city.

The Syrian government says groups linked to al-Qaeda or inspired by it have massive presence in Aleppo.

‘Constitutional mission to protect civilians’

Syrian President Bashar al-Assad said in a recent interview with a Swiss TV station that his government had a constitutional responsibility to clear Aleppo of terrorists.

"That's our mission, according to the constitution and the law, that we have to protect people; that we have to get rid of those terrorists from Aleppo. This is how we can protect the civilians," President Assad stated.

Aleppo, Syria's second largest city, has been divided between the government forces and foreign-backed militants since 2012. The Syrian army launched operations to reunite the government-held western part and the militant-held eastern section of Aleppo on September 22, with the support of the Russian air force.

Syrian soldiers patrol the area of Awijah as they advance in Aleppo's militant-held neighborhoods, October 8, 2016. (Photo by AFP)

The conflict in Syria, which began in March 2011, has claimed the lives of more than 400,000 people, according to an estimate by UN Special Envoy for Syria Staffan de Mistura.

Russia said on Tuesday that an airstrike by the US-led coalition purportedly fighting the Takfiri Daesh terrorists in Syria had killed six civilians.

The Russian military’s Reconciliation Center in Syria said the airstrike targeted the village of Hassajek in Aleppo province.

Russia says its military surveillance means spotted two Belgian F16 warplanes over the area at the time of the airstrike. Belgium denies that its aircraft struck the village.

Moscow says Russian and Syrian fighter jets are not flying over the area, in accordance with the decision to halt airstrikes on Aleppo.